How to use the 1rm calculator
Prepare the values for this calculation
Estimate one-repetition maximum from a submaximal weight and completed repetitions using common equations. Use the formula below to check that it answers your question. Read the input units before transferring figures from a statement, measurement or dataset.
Enter and check each input
- Weight lifted: enter a value at least 0. Use the unit named in the label or selected above. Do not leave this required field blank.
- Completed repetitions: enter a value at least 1 and no more than 36 and a whole number. Use the unit named in the label or selected above. Do not leave this required field blank.
- Formula: choose Epley, Brzycki, Lombardi. Match this selection to the data you enter.
The input table gives a complete example. Keep units and time periods consistent across related fields.
Calculate and resolve any input error
Choose Calculate after entering the values. Changes also update the answer after a short pause. If an error appears, follow its message, correct the field and calculate again. Reset restores the example values.
Interpret the answer
Check Estimated 1RM first. With the unchanged example inputs, it is 126.67. Compare the additional metrics with the primary result; each has its own label and unit.
Compare and keep a useful result
For a controlled comparison, keep every other example input unchanged and change Weight lifted from 100 to 110. The resulting Estimated 1RM is 139.33. This illustrates the equation’s response to that input, rather than a forecast of real events.
Read the chart’s axis labels and data table. A scenario curve changes one stated input while holding the others fixed; it does not add external observations. Use Download graph to save an available chart as a PNG.
Use Copy result or Download CSV to keep the answer. Share tool shares the page address without placing your input values in the URL. Recheck inputs and assumptions before using the result for a decision.
1RM Calculator formula
Epley: 1RM = weight × (1 + reps/30); Brzycki: 1RM = weight × 36/(37−reps).
Inputs and units
| Input | Format / range | Example |
|---|---|---|
| Weight lifted | minimum 0 | 100 |
| Completed repetitions | minimum 1; maximum 36; whole number | 8 |
| Formula | Select an option | Epley |
Worked example
Using the example inputs above, the estimated 1rm is 126.67.
- Estimated 1RM
- 126.67
- Formula
- epley
Results and assumptions
1RM equations are estimates; do not attempt unsafe maximal lifts solely because of a calculator result.
Fix an input or unexpected result
Weight lifted is required. Enter weight lifted using the format and bounds in the input table. Zero and an empty field are different: use zero only if it is allowed and represents your data.
If your answer differs from the example, choose Reset and compare every field, including selected units and options. Check percentage versus decimal entry and whether values describe the same period. Round only the final displayed answer when reproducing the formula.
If a discrepancy remains, report the calculator issue with the page address, non-sensitive example inputs, actual result, expected result and a reference for your calculation.